Production process for surface-mounting ceramic LED package, surface-mounting ceramic LED package produced by said production process, and mold for producing said package

ABSTRACT

The present invention is related to a surface-mounting ceramic LED package and a method for its production comprising: layering a ceramic green sheet which has a hole and a second ceramic green sheet, inserting a mold with a groove to form a partition in the bottom of the ceramic green sheet substrate, and firing the ceramic green sheet substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a production process for asurface-mounting ceramic light emitting diode (LED) package, asurface-mounting ceramic LED package produced by the production process,and a mold for producing the package.

2. Technical Background

LEDs are widely applied as backlighting for displays and light sourcesfor general illumination and the like. LED packages can be broadlyclassified into dome packages and surface-mounting packages. In the caseof the dome LED packages, an LED chip is mounted to a lead frame and theperiphery thereof is molded into the shape of a dome with resin. Thereason for molding the resin into the shape of a dome is to focus thelight from the chip forward by refraction, thereby improving the amountof radiated light. In the case of the surface-mounting packages, an LEDchip is placed in the bottom of a recess in a concave board and sealedwith resin. Since surface-mounting types allow lower mounting height,smaller size and lighter weight, they have a wide range of applicationsand have a promising future. In the case of surface-mounting types,instead of refracting light with a molded resin in the manner of dometypes, the walls of concave portions are facing upward (in the directionof the openings of the concave portions) and inclined so as to spreadout, thereby serving to enhance the amount of radiated light.

Since LED chips are able to radiate light of a plurality of colors, LEDdevices can be obtained that radiate various colors of light bycombining LED chips. However, when a plurality of LED chips is placedinside the same concave portion, there was the problem of light radiatedfrom a certain LED chip being interfered with by the light from anadjacent LED chip. For example, in the case of obtaining white light, amethod is employed that combines red (R), green (G) and blue (B) light.Ordinary LED chips are in the form of flat squares, and the lightradiating there from lacks directivity and is emitted from nearly theentire surface thereof. Since light radiated from the sides of a chipopposes light radiated from an adjacent chip, radiated light ofdifferent wavelengths interfere causing the light to be mutuallydiminished. This results in problems of attenuation of the amount ofradiated light and the occurrence of unevenness in the amount of light.In order to overcome this interference of light, a partition is providedin the bottom of the concave portions of surface-mounted LED devices inan attempt to reduce optical interference occurring between LED chips.

According to WO 2002/017401, the problem of a reduction in the amount oflight radiated from the entire LED device is overcome by providingpartitions between a plurality of LED chips in the bottom of concaveportions of a plastic LED device to prevent light radiated from one LEDchip from being interfered with by the light from another LED chip.

However, plastic is used for the package substrate in WO 2002/017401.Since plastic may be deteriorated by ultraviolet rays contained in lightemitted from LED chips, it is not optimal for use in LED packages. Inaddition, although high-output LED chips emit radiated light of highbrightness, the amount of heat dissipated also increases. Since plasticpackages lack heat resistance, thermal deterioration is considerablethereby resulting in the problem of a short service life of the packageitself.

On the other hand, although ceramic packages have superior heatresistance, they had the problem of being inferior to the mold abilityof plastic products with respect to fine structures such as inclined orcurved radiated light reflecting surfaces or partitions between chips.For this reason, ceramic packages have difficulty in guiding lightradiated from an LED chip in a desired direction, ultimately resultingin a loss in the amount of radiated light. Therefore, the shortcoming ofceramic packages having inferior mold ability with respect to finestructures was overcome by effectively utilizing the properties ofthermoplastic green sheets.

The present invention overcomes many of these problems by providing aproduction process for making a ceramic LED package, enabling partitionsto be formed both easily and reliably, making a ceramic LED packagehaving partitions, and making a mold for molding a ceramic LED package.

SUMMARY OF THE INVENTION

The production process for a surface-mounting ceramic LED package of thepresent invention comprises the steps of: (i) preparing a first ceramicgreen sheet and a second ceramic green sheet and forming through holesin the first ceramic green sheet; (ii) forming LED connection electrodesin the first and/or the second ceramic green sheet; (iii) layering thefirst ceramic green sheet and the second ceramic green sheet to form aceramic green sheet substrate having a concave portion; (iv) inserting amold, which comprises a base portion that presses portions other thanthe concave portion of the first ceramic green sheet of the ceramicgreen sheet substrate, and an insertion portion having a convex portionthat protrudes from the base portion and presses the inside of theconcave portion of the ceramic green sheet substrate, into the concaveportion of the ceramic green sheet substrate so that the distal endsurface of the convex portion contacts the bottom of the concave portionof the ceramic green sheet substrate, the distal end surface of theconvex portion of the mold being provided with a groove for forming apartition in the bottom of the concave portion of the ceramic greensheet substrate; (v) crimping the ceramic green sheets by pressing themold onto the ceramic green sheet substrate while at the same timepress-forming into a shape in which a partition is formed in the bottomof the concave portion of the ceramic green sheet substrate and thelateral surface of the concave portion is inclined so as to spreadtoward the opening; and (vi) firing the crimped and press-formed ceramicgreen sheet substrate to form a ceramic substrate.

In another embodiment of the present invention, the step (ii) is a step(called ii'herein), in which via holes are provided in the secondceramic green sheet, an electrically conductive paste is filled into thevia holes, and electrodes for achieving electrical continuity with theLED chip are formed in the surface of the second ceramic green sheet incontact with the first ceramic green sheet so as to cover the via holes;and the step (iii) is a step (iii′), in which the first ceramic greensheet is layered on the side of the second ceramic green sheet on whichthe electrodes have been formed to form a ceramic green sheet substratehaving concave portions.

Another embodiment of the present invention provides a productionprocess of a ceramic LED package comprising the following steps of: (I)preparing a ceramic green sheet and forming LED connection electrodes inthe ceramic green sheet using an electrically conductive paste; (II)contacting a mold with one side of the ceramic green sheet to form aconcave portion by pressing, the mold comprising an insertion portionhaving a convex portion and a base portion having an insertion portionhousing portion that houses the insertion portion, the insertion portionhaving a shape in which the apex of the convex portion is smaller thanthe bottom of the convex portion and the distal end surface of theconvex portion has a groove therein, and the concave portion beingformed so that a partition is formed in the bottom by the groove of themold and so as to spread in a direction of the opening thereof; and(III) firing the ceramic green sheet in which the conductor layer hasbeen formed.

Another embodiment provides a production process for making a ceramicLED package comprising the following steps of: (A) preparing a firstceramic green sheet and a second ceramic green sheet and forming throughholes in the first ceramic green sheet; (B) forming LED connectionelectrodes in the first ceramic green sheet and/or the second ceramicgreen sheet; (C) inserting and pressing a first mold into the throughholes of the first ceramic green sheet, the first mold comprising aninsertion portion having a convex portion and a base portion having aninsertion portion housing portion that houses the insertion portion, theinsertion having a shape in which the apex of the convex portion issmaller than the bottom of the convex portion, the convex portionprotruding from the base portion and being pressed so as to incline thewalls of the through holes, and the base portion pressing portions otherthan the through holes; (D) pressing a second mold onto one side of thesecond ceramic green sheet, the second mold being provided with a groovefor forming a partition in one side of the second ceramic green sheet,and a partition being provided in the surface of one side of the secondceramic green sheet by pressing with the mold; (E) layering the firstceramic green sheet and the second ceramic green sheet so that thepartition of the second ceramic green sheet is surrounded by the innerwalls of the through holes of the first ceramic green sheet; (F) thermalcompression bonding the first and the second ceramic green sheets toform a ceramic green sheet substrate having a concave portion; and (G)firing the press-formed and thermal compression bonded ceramic greensheet substrate to form a ceramic substrate.

Another aspect of the present invention is a surface-mounting ceramicLED package. This package has a ceramic substrate having a concaveportion, LED connection electrodes, and a partition provided in thebottom of the concave portion for separating the concave portion intotwo or more areas.

Another aspect of the present invention is a mold for producing asurface-mounting ceramic LED package. This mold comprises an insertionportion having a convex portion and a base portion having an insertionportion housing portion that houses the insertion portion. The mold hasa shape in which the apex of the convex portion is smaller than thebottom of the convex portion, and the distal end surface of the convexportion has a groove.

Other characteristics of the inventions, as described above, will beclear from the detailed description of the present specification.

According to the present production process of a ceramic LED package ofthe present invention, a ceramic LED package, in which decreases inemission rate caused by optical interference can be avoided even in thecase of having a plurality of LED chips, can be easily produced at goodyield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1H Describe, generally, the production process for surfacemounting a ceramic LED package.

FIGS. 2( a) and 2(b) show a second embodiment where a first ceramicgreen sheet and second ceramic green sheet are prepared and throughholes are formed in the first ceramic green sheet.

FIG. 2C shows via holes 202 and 204 formed in the second ceramic greensheet 104. FIG. 2D shows the layering of the first ceramic green sheetover a second ceramic green sheet on which the electrodes are formedfollowed by FIGS. 2E-H shows the further steps, as in steps 1A-AH, ofcarrying out the production process for surface mounting a ceramic LEDpackage.

FIGS. 3( a)-3(f) shows the preparation of a ceramic green sheet,formation of electrodes, and firing process for obtaining a ceramic LEDpackage.

FIGS. 4( a)-(k) describe a production process for surface mounting aceramic LED package wherein a first ceramic green sheet and secondceramic green sheet are produced separately and the resulting productsare crimped to obtain a substrate then fired.

FIG. 5 shows different views of a LED package and device.

FIG. 6 are various views of a ceramic LED package.

FIG. 7 shows various views of an additional electrode arrangement.

FIG. 8 shows views of another arrangement.

FIG. 9 shows overhead and other views of an LED package.

FIGS. 10A and 10B show examples of the shapes of electrodes.

FIG. 11 shows an embodiment with shaped partitions.

FIG. 12 shows the case of providing electrodes in areas separated bypartitions.

FIG. 13 is a perspective view of the mold of the present invention.

FIGS. 14A-14C describe various views of the invention.

FIGS. 15A-15F are view of the substrate from different angles showingthe insertion portions for the LED package.

DETAILED DESCRIPTION OF THE INVENTION

(I) Production Process of Surface-Mounting Ceramic LED Package

First Embodiment

A first aspect of the present invention is a production process of asurface-mounting ceramic LED package. A first embodiment of thisproduction process comprises the following steps:

-   (i) preparing a first ceramic green sheet and a second ceramic green    sheet, and forming through holes in the first ceramic green sheet,-   (ii) forming LED connection electrodes in the first and/or second    ceramic green sheet,-   (iii) layering the first ceramic green sheet and the second ceramic    green sheet to form a ceramic green sheet substrate having a convex    portion,-   (iv) inserting a mold, which comprises a base portion that presses    portions other than the concave portion of the first ceramic green    sheet of the ceramic green sheet substrate, and an insertion portion    having a convex portion that protrudes from the base portion and    presses the inside of the concave portion of the ceramic green sheet    substrate, into the concave portion of the ceramic green sheet    substrate so that the distal end surface of the convex portion    contacts the bottom of the concave portion of the ceramic green    sheet substrate, the distal end surface of the convex portion of the    mold being provided with a groove for forming a partition in the    bottom of the concave portion of the ceramic green sheet substrate,-   (v) crimping the ceramic green sheets by pressing the mold onto the    ceramic green sheet substrate while at the same time press-forming    into a shape in which a partition is formed in the bottom of the    concave portion of the ceramic green sheet substrate and the lateral    surface of the concave portion is inclined so as to spread in a    direction of the opening, and-   (vi) firing the crimped and press-formed ceramic green sheet    substrate to form a ceramic substrate.

Although the following provides an explanation of each step of the firstembodiment with reference to the drawings, the drawings are merelyexemplary and the present invention is not limited thereto. Furthermore,when necessary, the same reference symbols are used to indicate the sameconstituent members in the drawings of the present application.

A first embodiment of the production process of a surface-mountingceramic LED package of the present invention is explained with referenceto FIG. 1. FIGS. 1A to 1H are drawings for explaining the above steps(i) to (vi) of the present invention.

In step (i), as indicated in FIG. 1A, a first ceramic green sheet 102and a second ceramic green sheet 104 are first prepared. Next, as shownin FIG. 1B, through holes 106 are formed in the first ceramic greensheet 102 with a punch and the like. The through holes 106 can have anyshape corresponding to the application of the LED device. For example,in the case of viewing the through holes 106 from a first surface 108 ofthe first green sheet 102, the shape of the opening may be circular,oval or rectangular and the like, and in the case of forming the throughholes 106 with a punch and the like, the lateral surface 108 of thethrough holes 106 becomes a vertical lateral surface facing in thedirection of radiation of light of the LED, namely toward the firstsurface 108 from a second surface 110 of the first green sheet 102.

The size of the through holes 106 is required to be adjusted accordingto the size of an LED chip mounted on the LED package or according tothe number of LED chips mounted. It is necessary that the size of thethrough holes 106 be suitably adjusted according to the size of an LEDchip mounted on the LED package or according to the number of LED chipsmounted and the value of current that flows thereto. For example, in thecase of mounting four 0.3 W LED chips, the diameter of the through holeshas a size of 3 to 5 mm. A green sheet for low temperature co-firedceramics (LTCC) or a green sheet for high temperature co-fired ceramics(HTCC) can be used as materials of the first ceramic green sheet andsecond ceramic green sheet able to be used in the present invention.LTCC are composed by, for example, mixing and coating a ceramic rawmaterial powder composed of a mixture of powdered borosilicate glass andalumina powder, a binder composed of a thermoplastic acrylic resin andthe like, an organic solvent and water followed by molding. An HTCCgreen sheet has for a main component thereof alumina, aluminum nitride,mullite, cordierite, zirconia, magnesia or SiC fired at 1000° C. orhigher followed by the addition of an organic binder and plasticizer. Acommercially available LTCC or HTCC green sheet may be used in thepresent invention. The thickness of the first ceramic green sheet ispreferably 0.5 to 1.0 mm and more preferably 0.6 mm, and can be obtainedby, for example, layering two 0.3 mm green sheets. The second ceramicgreen sheet can be made to be of a similar thickness.

Next, in step (ii), electrodes 111 for achieving electrical continuitywith the LED chip are formed in advance on the first ceramic green sheetand/or the second ceramic green sheet.

FIG. 1C shows the case of having formed both poles of the electrodes onthe second ceramic green sheet. In addition, in the example of FIG. 1C,an electrode is formed for each region where an LED chip is mounted. Theformation of each electrode may be carried out by, for example, printingan electrically conductive paste using a conventional method such asscreen printing.

For example, a wiring pattern can be printed by placing a screen mask,in which a printing pattern is formed for printing a wiring pattern froma location where an LED is mounted to a connection terminal leading tothe outside, on a green sheet, supplying an electrically conductivepaste to the screen mask, and sliding a squeegee over the upper surfaceof the screen mask (not shown).

There are no particular limitations on the electrically conductive pasteprovided it is used for connecting an LED, and is composed of anelectrically conductive metal powder, resin and solvent. The resin usedin the electrically conductive paste is a cellulose-based resin oracrylic resin. The content of the resin and solvent is 5 to 25% byweight. The solvent is added to adjust the viscosity of the resin used.For example, a higher alcohol such as terpineol or ester thereof isadded. Examples of the electrically conductive metal powder includegold, platinum, silver, palladium, copper, nickel, rhodium, aluminum andalloys thereof. Since the firing temperature varies according to thetype of ceramic (LTCC or HTCC), it is necessary to select the type ofelectrically conductive metal powder accordingly. In the presentinvention, a commercially available electrically conductive pastecontaining silver (LT133, Dupont) for use with LTCC, tungsten ormolybdenum for use with HTCC, or paste containing a mixture of bothtypes of metal powders mixed with a cellulose-based resin and a solvent,for example, can be used for the electrically conductive paste used. Inaddition, in the case of forming both electrodes on the second greensheet, electrodes are arranged at the junctions between the firstceramic green sheet 102 and the second ceramic green sheet 104 to as toprovide a connection with the outside.

In addition, in another embodiment, as will be subsequently explained indetail in the section on a surface-mounting ceramic LED package as asecond aspect of the present invention, one of the electrodes (such asthe cathode) can be formed on the first green sheet, while the otherelectrode (such as the anode) can be formed on the second green sheet.In this case, one of the electrodes (such as the cathode) can be formedon the side of the first surface 108 of the first ceramic green sheet,and electrical continuity with an LED chip can be achieved with a wireconnection. In addition, in the present invention, electrodes may beprovided on both the first ceramic green sheet and the second ceramicgreen sheet.

Next, in step (iii), as shown in FIG. 1D, the first ceramic green sheet102 in which the through holes 106 are formed and the second ceramicgreen sheet 104 are layered to form a ceramic green sheet substrate 112having a concave portion.

In the case of having printed one of the electrodes on the first ceramicgreen sheet 102 in step (ii), the first and second ceramic green sheetsare joined so that this electrode is on the side of the first surface108 of the first ceramic green sheet. In addition, in the case of havingarranged both electrodes on the second ceramic green sheet, the firstand second ceramic green sheets are joined so that both electrodes areon the side where the first ceramic green sheet and the second ceramicgreen sheet are joined.

It is necessary to adjust the thickness of the ceramic green sheetsubstrate 112 according to desired strength and heat dissipationcharacteristics. If the substrate is too thin, the strength of theceramic substrate after firing decreases, while if too thick, theproblem results of difficulty in dissipating heat generated from the LEDchip. The thickness of the ceramic green sheet substrate can be adjustedby combining the thicknesses and number of the first and second ceramicgreen sheets.

The thickness of the ceramic green sheet substrate 112 is suitablyadjusted according to the power (output) of the LED chip. In the case ofchips that generate heat, a thin substrate is preferable from theviewpoint of dissipating heat. For example, in the case of mounting four0.3 W LED chips in through holes having a size of 3 to 5 mm, thethickness of the ceramic green sheet substrate 112 is preferably 1.0 to2.0 mm.

Next, as shown in FIG. 1E, step (iv) is a step in which a mold 114 isinserted into the through holes 106 of the ceramic green sheet substrate112. As will be subsequently explained in the section on a third aspectof the present invention, this mold 114 comprises an insertion portion118 having a convex portion 116, and a base portion 122 having aninsertion portion housing portion 120 that houses the insertion portion118, has a tapered shape in which the apex (distal end surface) 124 ofthe convex portion 116 is smaller than the bottom 126 of the convexportion, and a groove 128 is formed in the distal end surface of theconvex portion. Gaps are provided in the mold between the base portion122 and the insertion portion 118, enabling the insertion portion 118 toslide in the perpendicular direction with respect to the base portion122. In addition, surface irregularities may be formed in the lateralsurface of the mold and/or the inner peripheral surface of the groove,and surface irregularities in the lateral surface of the concave portionand/or a partition may be formed during the press forming of step (v)described below. A metal material, wood, heat-resistant resin or thelike that does not become deformed during press forming can be used forthe material of the mold.

This type of mold 114 is layered so that the convex portion 116 of themold is inserted into the concave portion 106 of the ceramic green sheetsubstrate.

Next, in step (v), as shown in FIG. 1F, the ceramic green sheetsubstrate and the mold described above are pressed. As a result of thispressing, the plurality of layered ceramic green sheets are mutuallycrimped thereby integrating the plurality of ceramic green sheets into asingle unit (FIG. 1G).

Although the conditions for pressing are adjusted according to thenumber of ceramic green sheets, the temperature range during pressing ispreferably 50 to 110° C., and the pressure 134 is preferably set to 5 to50 MPa.

In the present invention, the lateral surface of the convex portion 116of the mold insertion portion 118 has an inclined shape (tapered shape),and since the ceramic green sheets have a certain degree of plasticity,by pressing the convex portion 116 of the mold into the through holes106 possessed by the first ceramic green sheet, the inner peripheralsurfaces of the through holes 106 remember the shape of the inclined(tapered) lateral surface of the convex portion possessed by the mold.In this manner, in the ceramic green sheet substrate obtained throughstep (iv), although the inner peripheral surface (wall) 130 of theconcave portion is perpendicular to the first surface 108 of the firstceramic green sheet in the case of having formed through holes with apunch, for example, after being pressed with the mold, the innerperipheral surface 130 of the concave portion has an incline in which itspreads from the bottom 132 of the concave portion to the side of thefirst surface of the through holes of the first ceramic green sheet(also referred to as the opening side or opening direction in thepresent specification). In this manner, the inner peripheral surfaces ofthe through holes of the ceramic green sheet are molded to a shape thatcorresponds to the shape of the convex portion of the mold to bedescribed later. The angle of inclination θ1 of concave portion lateralsurface 130 (see FIG. 1G) is preferably 10 to 89 degrees. Since theceramic sheets have thermo plasticity, they soften and match the shapeof the mold when heated during pressing. The rigidity of the ceramicsheets returns when they are allowed to cool to the vicinity of roomtemperature following pressing, thereby enabling them to maintain theirformed shape. Furthermore, although the above explanation is of the caseof the lateral surface of the convex portion 116 of the mold beinginclined, the present invention is not limited thereto, but rather thelateral surface of the convex portion may also not be inclined. Inaddition, the inclined portion of the mold may have a linear or curveddirection of inclination. Radiation status can be controlled byadjusting the reflection angle of the light emitted from the LED.

In the present invention, a groove 128 can be provided in the distal endsurface 124 of the convex portion of the insertion portion 118 of themold 114. When provided with the groove 128 in this manner, a partition136 of a shape corresponding to the shape of the groove is formed in thebottom of the concave portion during press forming (FIG. 1G). The shapeand so forth of the partition is subsequently described in detail in thesection on a ceramic LED package (second aspect of the presentinvention).

In the past, when a conventional integrated convex portion type of moldhaving a plurality of convex portions is used when pressing a ceramicgreen sheet, there was the problem of the bottom of each of a pluralityof convex portions formed in a single ceramic green sheet substrate notbeing pressed with equal pressure due to the presence of protrusions inthe surface of the ceramic green sheets. In other words, although thebottoms of certain concave portions are adequately pressed to obtain aflat surface, in the bottoms of other concave portions, the distal endsurfaces of the convex portions of the mold are not pressed adequately,thereby resulting in the possibility of protrusions remaining in thesurface of ceramic green sheets. If the bottom of a concave portion isnot flat, the LED chip ends up inclining resulting in a decrease in theamount of radiated light and reducing yield during production of LEDpackages. In the invention of the present application, as a result ofusing the mold to be described later, the insertion portion 118 is ableto move independently of the base portion 122, thereby enabling thebottoms of a plurality of concave portions to be pressed evenly andallowing the obtaining of flat bottoms.

A hydrostatic press or hydraulic press is preferably used in the presentstep. A hydrostatic press or hydraulic press refers to that whichapplies pressure using a fluid to a pressurized article in a fluid suchas water or oil, and allows pressure to be applied uniformly throughoutthe entire pressurized article. At this time, although the ceramic greensheet substrate and mold are placed in a water-impermeable bag, it isnecessary to draw a vacuum within the bag to prevent the entry of airbubbles into the bag.

Furthermore, when using a hydrostatic or hydraulic press, it ispreferable to house a base plate in the bag for supporting the ceramicgreen sheet substrate, mold and green sheet substrate. When the ceramicgreen sheet substrate, mold and base plate in the bag are placed in ahydrostatic press and the ceramic green sheet substrate is clampedbetween the mold and the base plate, uniform pressure can be appliedfrom the back of the ceramic green sheet substrate enabling the back tohave a smoother finish.

Since the base plate is required to have adequate strength to withstandhigh pressure, it is preferably a metal plate made of iron, stainlesssteel or copper, or made of wood or heat-resistant resin and the likethat does not significantly deform during pressing when high pressure isapplied. Furthermore, the application of a small amount of a releaseagent such as silicone oil to the surfaces of the mold and base plateprior to pressing facilitates separation from the green sheet afterpressing.

In the production process of the present invention, in the case anelectrically conductive paste is printed for the electrodes 111 of thesecond green sheet, press forming is carried out after allowing theelectrically conductive paste to dry. Since the electrically conductivepaste is a mixture of electrically conductive metal powder and containsa resin and solvent, it has a certain degree of flexibility andplasticity even after drying. Thus, even if the mold is pressed onto theprinted electrically conductive paste from above, there is no breakageof the electrically conductive paste. For example, even in the case ofpressing a ceramic green sheet substrate having a thickness of 1.2 mm,on which is printed an electrically conductive paste at a thickness of10 to 15 μm, with the mold so that the apex of the convex portion of theinsertion portion is pressed to a depth of 50 μm from the surface of thesecond ceramic green sheet, there is no breakage of the electricallyconductive paste layer. In addition, the electrically conductive pastemay also be printed at a location where the partition 136 is formed. Insuch a case as well, there is no breakage of the electrodes due topressing for the same reasons as described above.

Next, in step (vi), the press-formed ceramic green sheet substrate isfired. The ceramic green sheet substrate is fired to obtain a ceramicLED package (see FIG. 1H). It is necessary to adjust the firingconditions in consideration of the type of green sheet and thetemperature and time at which the ceramic green sheet and the metalpowder in the electrically conductive paste printed on the green sheetare sintered. In the case silver powder is used in the electricallyconductive paste, firing conditions consist of a temperature ofpreferably 600 to 920° C. and more preferably 800 to 900° C. for 30minutes to 1.5 hours and a total time of 4 to 16 hours in the case ofLTCC green sheets, while firing conditions consist of a temperature ofpreferably 1200 to 1600° C. and more preferably 1300 to 1500° C. for 50minutes to 1 hour in the case of HTCC green sheets. Firing is carriedout with an ordinary belt oven or box oven and the like used for LEDpackages.

Second Embodiment

A second embodiment of the production process of the present inventionis the above-mentioned first embodiment, wherein the step (ii) is a step(ii′), in which via holes are provided in the second ceramic greensheet, an electrically conductive paste is filled into the via holes,and electrodes for achieving electrical continuity with the LED chip areformed in the surface of the second ceramic green sheet in contact withthe first ceramic green sheet so as to cover the via holes; and the step(iii) is a step (iii′), in which the first ceramic green sheet islayered on the side of the second ceramic green sheet on which theelectrodes have been formed to form a ceramic green sheet substratehaving concave portions.

Although the following provides an explanation of the second embodimentwith reference to the drawings, the drawings are merely exemplary andthe present invention is not limited thereto. FIG. 2 is a drawing forexplaining a production process of a ceramic LED package of the secondembodiment. Those steps other than step (ii′) and step (iii′) either usemeans similar to the previously described first embodiment, or can becarried out by a person with ordinary skill in the art by making knownchanges with respect to, for example, the pressure used during pressingor the firing conditions in the firing step.

In the second embodiment, a first ceramic green sheet and a secondceramic green sheet are prepared, and through holes 106 are formed inthe first ceramic green sheet in the same manner as the above-mentionedstep (i) (see FIGS. 2A and 2B).

In step (ii′), via holes 202 and 204 are formed in the second ceramicgreen sheet, an electrically conductive paste 206 is filled therein, andelectrodes 208 for achieving electrical continuity with an LED chip areformed in the second ceramic green sheet (see FIG. 2C).

The via holes 202 and 204 may be formed by a method such as punching atpredetermined locations of the second ceramic green sheet 104.

Although there are no particular limitations on the size of the viaholes, the cross-sectional area thereof is preferably large enough forenhancing heat dissipation efficiency within a range that maintainscavity strength. More specifically, in the case of the surface area ofthe bottom of the cavity being 7.0 mm², for example, the second ceramicgreen sheet preferably has 8 to 11 via holes having a diameter of 200 to400 μm.

Next, an electrically conductive paste is filled into the formed viaholes 202 and 204 to form electrodes 208 for achieving electricalcontinuity with an LED. Filling of the electrically conductive paste andformation of the electrodes are typically carried out by printing suchas screen printing. Further, wiring may also be carried out foracquiring electrical continuity with the outside. Filling of the viaholes 202 and 204 of the second ceramic green sheet 104 and formation ofthe electrodes 208 may be carried out simultaneously from the viewpointof reducing production cost.

Next, in step (iii′), the first ceramic green sheet 102 is layered overthe side of the second ceramic green sheet 104 on which the electrodes208 are formed to form a ceramic green sheet substrate 112 havingconcave portions (see FIG. 2D).

The various conditions for the first ceramic green sheet, the secondceramic green sheet, the electrically conductive paste and the like inthe steps (ii′) and (iii′) described above are as explained for thefirst embodiment.

The steps (IV) to (VI) explained in the first embodiment are thencarried out following the above steps (see FIGS. 2E to 2H).

According to the production process of the present invention asdescribed above, a surface-mounting ceramic LED package can be producedhaving electrodes, a partition, a concave portion (having apredetermined angle of the lateral surface thereof (74 1=10 to 89degrees)) and the like.

Third Embodiment

A third embodiment of the production process of the present invention isa process in which a concave portion having a partition is formeddirectly in a ceramic green sheet. More specifically, this processcomprises the steps of:

-   (I) preparing a ceramic green sheet and forming LED connection    electrodes in the ceramic green sheet using an electrically    conductive paste;-   (II) contacting a mold with one side of the ceramic green sheet to    form a concave portion by pressing, the mold comprising an insertion    portion having a convex portion and a base portion having an    insertion portion housing portion that houses the insertion portion,    the insertion portion having shape in which the apex of the convex    portion is smaller than the bottom of the convex portion and the    distal end surface of the convex portion having a groove therein,    and the concave portion being formed so that a partition is formed    in the bottom by the groove of the mold and so as to spread in a    direction of the opening thereof; and-   (III) firing the ceramic green sheet in which the conductor layer    has been formed.

Although the following provides an explanation of each step of the thirdembodiment with reference to the drawings, the drawings are merelyexemplary and the present invention is not limited thereto.

The third embodiment of a production process of a surface-mountingceramic LED package of the present invention is explained with referenceto FIG. 3. FIGS. 3A to 3F are drawings for explaining theabove-mentioned steps (I) to (III) of the present invention.

First, in step (I), as shown in FIG. 3A, a ceramic green sheet 102 isprepared. The ceramic green sheet may consist of a plurality of ceramicgreen sheets layered and pressed together in order to ensure therequired film thickness.

Next, electrodes for achieving electrical continuity with an LED chip inadvance are formed in the prepared ceramic green sheet. As shown in FIG.3B, formation of the electrodes can be carried out by forming electrodes208 using an electrically conductive paste followed by achievingelectrical continuity through via holes 206. Electrically conductivepaste is also filled into the via holes 206. Although the example ofFIG. 3B shows the formation of electrodes 208 and via holes 206, onlyelectrodes may be formed as in the previously described firstembodiment.

In the production process of the present invention, the electricallyconductive paste can be formed by printing. The electrically conductivepaste is as explained in the first embodiment. A method known in theprior art such as screen printing can be applied for the screeningmethod.

The conditions for forming the electrodes and via holes are as explainedin the previously described first and second embodiments.

Next, as shown in FIG. 3C, a mold 114 is contacted with the ceramicgreen sheet 102. This mold is the same as that explained in theproduction process of the first embodiment. This mold 114 is layeredover the ceramic green sheet 102 so that a convex portion 116 of themold contacts one side of the ceramic green sheet 102.

Next, as shown in FIG. 3D, the mold is pressed onto the ceramic greensheet in the state described above. As a result of this pressing, theconcave portion 106 having a partition 136 in the bottom thereof isformed in the ceramic green sheet (FIG. 3E).

Although pressing conditions are adjusted according to the number ofceramic green sheet substrates, the temperature range thereof ispreferably 50 to 110° C. and the setting for pressure 134 is preferably5 to 50 MPa.

In the present invention, as was previously described, the lateralsurface of the convex portion 116 of the insertion portion 118 of themold has an inclined (tapered) shape, and since the ceramic green sheetis provided with a certain degree of plasticity, a concave portion isformed in the ceramic green sheet having a wall that coincides with theshape of the inclined (tapered) lateral surface of the convex portion ofthe mold. In this manner, in the ceramic green sheet substrate obtainedin this step, the inner peripheral surface (wall) 130 of the concaveportion is of a shape having an incline that spreads toward the openingof the ceramic green sheet from the bottom 132 of the concave portionafter being pressed with the mold. In this manner, the inner peripheralsurface of the wall of the ceramic green sheet is molded to a shapecorresponding to the shape of the convex portion of the mold to bedescribed later. The angle of inclination θ1 of concave portion lateralsurface 130 (see FIG. 3E) is preferably 10 to 89 degrees. Since theceramic green sheet has thermo plasticity, it softens and matches theshape of the mold when heated during pressing. The rigidity of theceramic green sheet returns when it is allowed to cool to the vicinityof room temperature following pressing, thereby enabling it to maintainits formed shape. Furthermore, although the above explanation is of thecase of the lateral surface of the convex portion 116 of the mold beinginclined, the present invention is not limited thereto, but rather thelateral surface of the convex portion may also not be inclined. Inaddition, the inclined portion of the mold may have a linear or curveddirection of inclination. Radiation status can be controlled byadjusting the reflection angle of the light emitted from the LED.

In the present invention, a groove 128 can be provided in the distal endsurface 124 of the convex portion of the insertion portion 118 of themold 114. When provided with the groove 128 in this manner, a partition136 of a shape corresponding to the shape of the groove is formed in thebottom of the concave portion during press forming (FIG. 3E). The shapeand so forth of the partition is subsequently described in detail in thesection on a ceramic LED package (second aspect of the presentinvention).

In this third embodiment, as well, a hydrostatic press or hydraulicpress is preferably used when pressing the ceramic green sheet.

Furthermore, when using a hydrostatic or hydraulic press, it ispreferable to house a base plate in a bag for supporting the ceramicgreen sheet substrate, mold and green sheet substrate. When the ceramicgreen sheet substrate, mold and base plate in the bag are placed in ahydrostatic press and the ceramic green sheet substrate is clampedbetween the mold and the base plate, uniform pressure can be appliedfrom the back of the ceramic green sheet substrate enabling the back tohave a smoother finish.

The base plate is as explained in the description of the firstembodiment.

Next, in step (III), the ceramic green sheet on which a conductor layerhas been formed is fired. In this step, the ceramic green sheet is firedto obtain a ceramic LED package (see FIG. 3F). It is necessary to adjustthe firing conditions by taking into consideration the temperature andtime at which the ceramic green sheet is fired according to the type ofgreen sheet, metal powder contained in the electrically conductive pasteprinted on the green sheet and so forth. In the case where silver powderis used in the electrically conductive paste, firing conditions consistof a temperature of preferably 600 to 920° C. and more preferably 800 to900° C. for 30 minutes to 1.5 hours and a total time of 4 to 16 hours inthe case of LTCC green sheets, while firing conditions consist of atemperature of preferably 1200 to 1600° C. and more preferably 1300 to1500° C. for 50 minutes to 1 hour in the case of HTCC green sheets.Firing is carried out with an ordinary belt oven or box oven and thelike used for LED packages.

A fourth embodiment of the production process of the present inventionis a process for producing a surface-mounting ceramic LED package of thefirst embodiment, wherein a first ceramic green sheet and a secondceramic green sheet are processed separately, and the resultingprocessed products are crimped to obtain a ceramic green sheet substratefollowed by firing the resulting ceramic green sheet substrate. Morespecifically, this process comprises the steps of:

-   (A) preparing a first ceramic green sheet and a second ceramic green    sheet and forming through holes in the first ceramic green sheet;-   (B) forming LED connection electrodes in the first ceramic green    sheet and/or the second ceramic green sheet;-   (C) inserting and pressing a first mold into the through holes of    the first ceramic green sheet, the first mold comprising an    insertion portion having a convex portion and a base portion having    an insertion portion housing portion that houses the insertion    portion, the insertion portion having a shape in which the apex of    the convex portion is smaller than the bottom of the convex portion,    the convex portion protruding from the base portion and being    pressed so as to incline the walls of the through holes, and the    base portion pressing portions other than the through holes;-   (D) pressing a second mold onto one side of the second ceramic green    sheet, the second mold having a convex portion and being provided    with a groove on the distal end surface of the convex portion for    forming a partition in one side of the second ceramic green sheet,    and a partition being provided in the surface of one side of the    second ceramic green sheet by pressing with the mold;-   (E) layering the first ceramic green sheet and the second ceramic    green sheet so that the partition of the second ceramic green sheet    is surrounded by the inner walls of the through holes of the first    ceramic green sheet;-   (F) thermal compression bonding the first and the second ceramic    green sheets to form a ceramic green sheet substrate having a    concave portion; and (G) firing the press-formed and thermal    compression bonded ceramic green sheet substrate to form a ceramic    substrate.

In step (A), as shown in FIG. 4A, a first ceramic green sheet 102 and asecond ceramic green sheet 104 are first prepared. The materials andother conditions of the first and second ceramic green sheets are aspreviously explained in the first embodiment. Next, as shown in FIG. 4B,through holes 106 are formed with a punch and the like in the firstceramic green sheet 102. The shape, dimensions and other conditions ofthe through holes 106 are the same as in the first embodiment.

Next, in step (B), as shown in FIG. 4C, electrodes are formed on thefirst ceramic green sheet and/or second ceramic green sheet. Anelectrically conductive paste is used to form the electrodes. In FIG.4C, the example is shown of forming electrodes 208 on the side of thesecond ceramic green sheet pressed by the mold. As shown in FIG. 4C, forexample, formation of the electrodes can be carried out by formingelectrodes 208 using an electrically conductive paste and achievingelectrical continuity through via holes 206. Electrically conductivepaste is also filled into the via holes 206. Although FIG. 4C shows anexample of forming both electrodes 208 and through holes 206, onlyelectrodes 208 may be formed as in the first embodiment. In addition, inthe present invention, the electrodes can be provided on only the firstceramic green sheet, only the second ceramic green sheet or both.

In the production process of the present invention, the components ofthe electrically conductive paste, composition thereof, coating methodof the electrically conductive paste, film thickness after coating andthe like are as described in the first embodiment.

Next, in step (C), as shown in FIG. 4D, a first mold 114 is insertedinto the through holes 106 of the first ceramic green sheet 102. As willbe explained in a third aspect of the present invention to be describedlater, this mold comprises an insertion portion 118 having a convexportion 116, and a base portion 122 having an insertion portion housingportion 120 that houses the insertion portion 118, and the convexportion 116 has a tapered shape such that the apex (distal end surface)124 of the convex portion is smaller than the bottom 126 of the convexportion. In the present embodiment, differing from the first to thirdembodiments, it is not necessary to form a groove in the apex of theconvex portion of the mold. However, a mold similar to that used in thefirst to third embodiments can be used. The mold 114 has a structure andcomposition, including materials, as explained in the first embodimentwith the exception of not forming a groove in the apex of the convexportion.

This mold 114 is layered such that the convex portion 116 of the mold isinserted into the through holes 106 of the ceramic green sheetsubstrate.

Next, as shown in FIG. 4E, the first ceramic green sheet and the moldare pressed. As a result of this pressing, an incline is provided in thewalls of the through holes 106 of the first ceramic green sheet 102(FIG. 4F).

Although the pressing conditions are adjusted according to the type offirst ceramic green sheet, the temperature range is preferably 50 to110° C., and the pressure 134 is preferably set to 5 to 50 MPa.

In the present invention, as previously described, since the lateralsurface of the convex portion 116 of the insertion portion 118 of themold have an inclined (tapered) shape, and the ceramic green sheet has acertain degree of plasticity, as a result of pressing the convex portion116 of the mold into the through holes 106 possessed by the firstceramic green sheet and applying pressure, the inner peripheral surfacesof the through holes 106 remember the shape of the inclined (tapered)lateral surface of the convex portion possessed by the mold. In thismanner, in the first ceramic green sheet obtained in step (C), althoughthe inner peripheral surfaces (walls) 130 of the through holes 106thereof are perpendicular to the first surface 108 of the first ceramicgreen sheet in the case of having formed the through holes with a punch,for example, after being pressed with the mold, an incline of apredetermined angle is formed in the lateral surface 130 of the concaveportion. This angle of inclination θ1 (see FIG. 4F) is preferably 10 to89 degrees. Since the ceramic sheets have thermoplasticity, they softenand match the shape of the mold when heated during pressing. Therigidity of the ceramic sheets returns when they are allowed to cool tothe vicinity of room temperature following pressing, thereby enablingthem to maintain their formed shape. Furthermore, although the aboveexplanation is of the case of the lateral surface of convex portion 116of the mold being inclined, the present invention is not limitedthereto, but rather the lateral surface of the convex portion may alsonot be inclined. In addition, the inclined portion of the mold may havea linear or curved direction of inclination. Radiation status can becontrolled by adjusting the reflection angle of the light emitted fromthe LED.

Next, in step (D), a second mold is pressed onto one side of thepreviously prepared second ceramic green sheet. As a result, apredetermined structure such as a partition is imparted to one side ofthe second ceramic green sheet (FIGS. 4G to 4K).

As shown in FIG. 4G, the mold 114′ used in this step has a plurality ofgroove 128 on one side. A conventional mold in the form of the mold 114′can be used for the pressing of this step. A metal material, wood,heat-resistant resin or the like that does not become deformed duringpress forming can be used for the material of the mold.

This mold 114′ is layered such that the side of the mold that has aplurality of groove 128 contacts one side of the second ceramic greensheet followed by pressing (FIG. 4H). The pressing conditions consist ofa pressure of 5 to 50 MPa. A partition 136 is formed on the side of thesecond ceramic green sheet pressed by the mold 114′ as a result of thepressing of this step (FIG. 41).

Next, in step (E) and (F), the first ceramic green sheet and the secondceramic green sheet are superimposed and bonded (FIG. 4J). An adhesivesuch as solvent or resin medium may be preferably used between the firstand the second ceramic green sheet to bond them. Or, crimping such ashydrostatic pressure, hydraulic press or just plane press may bepreferably used. In the case of hydrostatic pressure, hydraulic press,the ceramic green sheet are preferably slipped in between two boardbefore being put in the bag so that the formed partition would not becrashed by vacuuming. During this superimposition, the partition of thesecond ceramic green sheet are made to be surrounded by the inner wallsof the through holes 106 of the first ceramic green sheet.

Next, in step (G), the ceramic green sheet substrate obtained in step(F) is fired. The firing method and conditions are as explained in thefirst embodiment.

(II) Ceramic LED Package

A second aspect of the present invention is a ceramic LED package.

The ceramic LED package of the present invention is a surface-mountingceramic LED package having a ceramic substrate having a concave portion,LED connection electrodes and a partition provided in the bottom of theconcave portion for separating the concave portion into two or moreareas.

In the present invention, one or a plurality of partitions can beprovided in the bottom of the concave portion. The partition may extendin a straight line from one point on the bottom of the concave portiontoward another point, or may extend radially from a single point on thebottom of the concave portion, thereby separating the bottom of theconcave portion into two or more areas. In addition, the thickness ofthe partition preferably increases from the opening of the concaveportion toward a site in contact with the bottom of the concave portion.

In the present invention, the inner peripheral surface of the concaveportion of the ceramic substrate and the surface of the partitionpreferably has surface irregularities.

Although the following provides an explanation of preferred embodimentsof the ceramic LED package of the present invention with reference toFIGS. 5 to 12, these are merely exemplary, and the present invention isnot limited thereto.

An example of a ceramic LED package of a first embodiment is explainedusing FIGS. 5 to 8. FIG. 5A is an overhead view of a ceramic LED package300, while FIG. 5B is a cross-sectional view taken along line 5B of FIG.5A. In addition, FIG. 5C is a drawing showing a ceramic LED package(ceramic LED device) mounted with LED chips. FIGS. 6 to 8 are drawingsshowing examples of the shape of electrodes of the ceramic LED packageof the first embodiment. Furthermore, the description of the electrodesis omitted in FIG. 5.

In this embodiment, the ceramic LED package 300 has a ceramic substrate138, a concave portion 304 formed roughly in the center thereof, and apartition 308 provided in the bottom 306 of the concave portion 304. Alateral surface 310 of the concave portion 304 has an incline thatspreads toward the opening of the concave portion from the bottom 306thereof. As a result of having this incline, the efficiency of radiationof light from the LED devices is improved. This angle of inclination θ1(see FIG. 5B) is preferably 10 to 89 degrees. In addition, the inclinedwall may have a curved direction of inclination instead of a lineardirection of inclination. Since the ceramic LED package of the presentinvention uses ceramic for the substrate, it is resistant todeterioration by ultraviolet light while also having superior heatdissipation characteristics.

The partition 308 provided in the bottom of the concave portion preventslight radiated from each LED chip from mutually interfering in an LEDdevice installed with a plurality of colored LED chips. There are noparticular limitations on the shape of the partition provided it is ableto separate the concave portion into a plurality of areas. For example,FIG. 5 shows an example of a rectangular partition (referred to as a Ior I-shaped partition in the present specification) extending in astraight line from a point 316 on the bottom of the concave portiontoward another point 318.

In the present invention, as will be explained in the second and thirdembodiments, the partition can have a shape such that it extends, forexample, radially from one point on the bottom of the concave portiontoward a plurality of other points. Although two LED chips arepreferably mounted in the case of the I-shaped partition of the firstembodiment (see FIG. 5C), an additional number of LED chips can bemounted as necessary. As shown in FIG. 5C, as a result of providing thepartition 308 between an LED chip (e.g., blue LED chip) 312 and an LEDchip (e.g., red LED chip) 314, the blue and red light respectivelyradiated from each chip is guided to the side of the opening withoutmutually interfering.

In the specification of the present application, a ceramic LED packagerefers to that not mounted with an LED chip as shown in FIGS. 5A and 5B,while a ceramic LED device refers to that mounted with LED chips asshown in FIG. 5C.

Next, an explanation is provided of the electrodes of the ceramic LEDpackage of the present invention with reference to FIGS. 6 to 8. FIG. 6Ais an overhead view, while FIGS. 6B and 6C are cross-sectional viewstaken along line 6B of FIG. 6A. Furthermore, FIG. 6C shows an example ofthe case of having provided electrodes when acquiring an electricalconnection with the outside on the bottom of a ceramic substrate.

The ceramic LED package of the first embodiment of the present inventionhas an I-shaped partition. In this embodiment, as shown in FIGS. 6A and6B, electrodes consisting of cathodes 402 and 402′ and anodes 404 and404′ are respectively provided in two areas separated by the partition308. In FIG. 6, although the electrodes are formed so as to occupynearly the entirety of each area, the present invention is not limitedthereto, but rather the electrodes are only required to at least beformed at those portions where electrical continuity is able to beachieved with the LED chips. In FIGS. 6B and 6C, although an example isshown in which electrical continuity is acquired with the outside byforming via holes 202 and 204 containing conductors in the ceramicsubstrate, in the present invention, electrical continuity may also beacquired with the outside by wiring the electrodes within the ceramicsubstrate instead of forming via holes. In addition, electrodes 408 mayalso be provided on the bottom 406 of the ceramic substrate.

Next, an explanation is provided of another electrode arrangementpattern with reference to FIG. 7. FIG. 7A is an overhead view, whileFIG. 7B is a cross-sectional view taken along line 7B of FIG. 7A. Asshown in FIG. 7, via holes 202 and 204 containing conductors areprovided in ceramic substrate 138, and a cathode 502 and an anode 504are provided So as to be connected with the conductors of the via holes.In this example, the electrodes are wired so as cover the partition andextend across a plurality of areas. Furthermore, as was also explainedin the previously described production process of the present invention,although the electrodes are printed followed by forming the partition bypressing with a mold in the present invention, at this time theelectrodes are formed so as to cover the partition as shown in FIG. 7Bafter sintering, for example, without being severed by the groove of themold.

Next, an explanation is provided of still another electrode arrangementpattern with reference to FIG. 8. FIG. 8A is an overhead view, whileFIG. 8B is a cross-sectional view taken along line 8B of FIG. 8A. FIG.8C is a cross-sectional view of an example in which LED chips 608 and610 are mounted on the package of FIG. 8A.

As shown in FIG. 8, via holes 202 and 204 containing conductors areprovided in the ceramic substrate 138, and an anode 604 is provided soas to be connected with the conductors of the via holes. In addition,cathodes 602 and 602′ are provided on the side of the opening of concaveportion 306 of the ceramic substrate. In this example, the LED chip andcathodes 602 and 602′ are connected by wires 612. The anode 604 of thisexample is arranged over the entire surface so as to extend across aplurality of areas while covering the partition. Furthermore, in thisexample as well, the anode 604 is formed so as to cover the partition asshown in FIG. 8B after sintering, for example, without being severed.

Second Embodiment

The following provides an explanation of an example of a secondembodiment of the ceramic LED package according to FIGS. 9 and 10.

FIG. 9A is an overhead view of a ceramic LED package 700, while FIG. 9Bis a cross-sectional view taken along line 9B of FIG. 9A. In addition,FIG. 9C shows a ceramic LED package mounted with LED chips (ceramic LEDdevice). FIGS. 10A and 10B are drawings showing examples of the shapesof the electrodes of the ceramic LED package of the second embodiment.Furthermore, a description of the electrodes is omitted in FIG. 9.

In this embodiment, the ceramic LED package 700 has a ceramic substrate138, a concave portion 304 formed in roughly the center thereof, and apartition 702 provided in the bottom 306 of the concave portion. Theshape of the lateral surface 310 of the concave portion 304, theinclination angle (θ1) and other characteristics are the same as in thefirst embodiment.

There are no particular limitations on the shape of the partition 702provided in the bottom of the concave portion provided it is able toseparate the concave portion into a plurality of areas. For example,FIG. 9 shows an example of providing a Y (or Y-shaped) partition in thecenter of the bottom of the concave portion.

In the specification of the present application, the state of thepartition extending in the form of a plurality of straight or curvedlines from a specific point on the bottom of the concave portion towardthe lateral surface of the concave portion is defined as “extendingradially”. For example, in the example shown in FIG. 9A, the partition702 extends linearly and radially from a point 316 on the bottom of theconcave portion toward the lateral surface 310 of the concave portion,namely toward a plurality of other points (in this case, 3 points) 318,318′ and 318″.

The partition prevents light radiated from each LED chip from mutuallyinterfering in an LED device installed with a plurality of colored LEDchips in the same manner as in the first embodiment.

In the case of the Y-shaped partition of the second embodiment, althoughthree LED chips are preferably mounted (see FIG. 9C), an additionalnumber of LED chips can be mounted as necessary. As shown in FIG. 9C, asa result of providing the partition 702 between an LED chip (e.g., blueLED chip) 704, an LED chip (e.g., red LED chip) 706 and an LED chip(e.g., green LED chip) 708, decreases in brightness of the blue, red andgreen light respectively radiated from each chip are inhibited withoutmutually interfering.

Next, an explanation is provided of the electrodes of the ceramic LEDpackage of the present invention with reference to FIG. 10. FIG. 10Ashows the case of respectively providing electrodes in areas separatedby a partition, while FIG. 10B shows the case of forming electrodes overthe entire concave portion irrespective of the partition.

The ceramic LED package of the second embodiment of the presentinvention has a Y-shaped partition. In this embodiment, as shown in FIG.10A, the electrodes are respectively provided in the form of cathodes710 and anodes 712 in three areas separated by a partition 702. In thepresent embodiment as well, each electrode is not required to be formedover the entirety of each area separated by the partition, but is onlyrequired to at least be formed in those areas where electricalcontinuity is able to achieved with the LED chips.

Next, an explanation is provided of another electrode arrangementpattern (case of forming the electrodes over the entire concave portionirrespective of the partition) with reference to FIG. 10B. As shown inFIG. 10B, cathode 710 and anode 712 are provided with an insulatingportion 714 there between in the central area of the concave portion ofceramic substrate 138 and on the side of the lateral surface 310 of theconcave portion of the area thereof, respectively. In this example aswell, the electrodes are arranged covering the partition so as to extendacross a plurality of areas. Furthermore, as was also explained in thepreviously described production process of the present invention,although the electrodes are printed followed by forming the partition bypressing with a mold in the present embodiment as well, at this time theelectrodes are formed so as to cover the partition without being severedby the groove of the mold.

Third Embodiment

The following provides an explanation of an example of a ceramic LEDpackage of a third embodiment according to FIGS. 11 and 12. FIG. 11A isan overhead view of a ceramic LED package 900, while FIG. 11B is across-sectional view taken along line 11B of FIG. 11A. In addition, FIG.11C shows a ceramic LED package mounted with LED chips (ceramic LEDdevice). FIGS. 1 2A and 1 2B are drawings showing examples of the shapesof electrodes of the ceramic LED package of the third embodiment.Furthermore, a description of the electrodes is omitted in FIG. 11.

In this embodiment, the ceramic LED package 900 has a ceramic substrate138, a concave portion 304 formed in roughly the center thereof, andpartitions 902 and 904 provided in the bottom 306 of the concaveportion. The shape of the lateral surface 310 of the concave portion304, the inclination angle (θ1) and other characteristics are the sameas in the first embodiment.

There are no particular limitations on the shape of the partitions 902and 904 provided in the bottom of the concave portion provided they areable to separate the concave portion into a plurality of areas. Forexample, FIG. 11 shows an example of providing + (plus) (or +-shaped)partitions in the center of the bottom of the concave portion. As shownin FIG. 11A, partitions 902 and 904 extend radially toward the lateralsurface 310 of the concave portion from a single point 316 on the bottomof the concave portion, namely toward a plurality of other points (inthis case, 4 other points) 318, 318′, 318″ and 318′″.

The partitions prevent light radiated from each LED chip from mutuallyinterfering in an LED device installed with a plurality of colored LEDchips in the same manner as in the first and second embodiments.

In the case of the +-shaped partitions of the third embodiment, althoughfour LED chips are preferably mounted (see FIG. 11C), an additionalnumber of LED chips can be mounted as necessary. As shown in FIG. 11C,as a result of providing the partitions 902 and 904 between an LED chip(e.g., blue LED chip) 906, an LED chip (e.g., green LED chip) 908, anLED chip (e.g., red LED chip) 910 and an LED chip (e.g., green LED chip)912, decreases in brightness of the blue, green and red lightrespectively radiated from each chip are inhibited without mutuallyinterfering.

Next, an explanation is provided of the electrodes of the ceramic LEDpackage of the present invention with reference to FIG. 12. FIG. 12Ashows the case of respectively providing electrodes in areas separatedby partitions, while FIG. 12B shows the case of forming electrodes overthe entire concave portion irrespective of the partitions.

The ceramic LED package of the third embodiment of the present inventionhas +-shaped partitions. In this embodiment, as shown in FIG. 12A, theelectrodes are respectively provided in the form of cathodes 1002 andanodes 1004 in four areas separated by the partitions 902 and 904.

Next, an explanation is provided of another electrode arrangementpattern (case of forming the electrodes over the entire concave portionirrespective of the partitions) with reference to FIG. 12B. As shown inFIG. 12B, cathodes 1002 and anodes 1004 are each provided with aninsulating portion 1006 there between in the central area of the concaveportion of ceramic substrate 138 and on the side of the lateral surface310 of the concave portion of the area thereof. In this example as well,the electrodes are arranged covering the partitions so as to extendacross a plurality of areas. Furthermore, as was also explained in thepreviously described production process of the present invention,although the electrodes are printed followed by forming the partitionsby pressing with a mold in the present embodiment as well, at this timethe electrodes are formed so as to cover the partitions without beingsevered by the groove of the mold.

Although the preceding explanations have provided explanations ofspecific embodiments of the ceramic LED package of the presentinvention, the present invention is not limited thereto, but rather, forexample, the partition is not required to be I-shaped, Y-shaped or+-shaped as described above, but instead can separate the bottom of theconcave portion into a plurality of areas by forming partition extendingin a straight line or curved line from a single point on the bottom ofthe concave portion toward a plurality of other points. Furthermore,although the cases in the examples described above depict the partitionshaving a slight gap of about, for example, 0.5 mm from the lateralsurface of the concave portion without being formed so as to contact thelateral surface of the concave portion, the present invention is notlimited thereto, but rather the partitions can also be formed so as tocontact the lateral surface of the concave portion so as to divide theconcave portion into two or more areas. The length of the partitions islonger than the LED chips. In addition, in the case of mounting LEDchips, the LED package of the present invention is applicable not onlyto the case of simultaneously illuminating all LED chips, but also tothe case of illuminating each LED chip separately. The shape of theelectrodes is not limited to each of the embodiments described above,but rather can have a shape applicable to simultaneously illuminatingall LEDs or illuminating each LED chip separately.

(III) Mold

A third aspect of the present invention is a mold for producing theceramic LED package of the present invention. The mold of the presentinvention comprises an insertion portion having a convex portion and abase portion having an insertion portion housing portion that houses theinsertion portion, has a shape (tapered shape) in which the apex of theconvex portion is smaller than the bottom of the convex portion, and thedistal end surface of the convex portion has a groove. The sidewalls ofthe groove are able to be inclined so that the opening of the groove iswider than the bottom. A gap is provided between the insertion portionand the base portion. As a result of composing in this manner, theconvex portion is able to slide perpendicular to the base portion. Thelateral surface of the convex portion and/or the groove may have finesurface irregularities in the surface thereof. In addition, the materialof the mold is a metal material, wood or heat-resistant resin that doesnot significantly deform during pressing.

In another embodiment, the mold of the present invention does not have agroove in the apex of the convex portion. In still another embodiment,the convex portion of the mold of the present invention does not have atapered shape while the distal end surface of the convex portion has agroove.

Although the following provides an explanation of the mold of thepresent invention with reference to FIGS. 13 and 14, these are merelyexemplary of the present invention, and the present invention is notlimited thereto. FIG. 13A is a perspective view of the mold of thepresent invention, FIG. 13B is an exploded perspective view of FIG. 13A,and FIG. 13C is a partially enlarged view of a groove 128. In addition,FIG. 14A is an overhead view of the mold of FIG. 13A, FIG. 14B is across-sectional view taken along line 14B of FIG. 14A, and FIG. 14Cshows a state in which an insertion portion has slid in FIG. 14B.

As shown in FIGS. 13A to 13C and FIGS. 14A to 14C, a mold 1100 comprisesan insertion portion 118 having a convex portion 116, and a base portion122 having an insertion portion housing portion 120 that houses theinsertion portion 118. The convex portion 116 has the shape of acircular truncated cone in which the apex (distal end surface) 124 ofthe convex portion is smaller than a bottom 126 of the convex portion(namely, the cross-section thereof has a tapered shape). In addition,the mold has a groove 128 on the distal end surface 124 of the convexportion.

In addition, portions other than groove 128 of the distal end surface124 of the convex portion are in a plane parallel with the surface 1106on the side having the convex portion of base portion 122 (also referredto as the base portion front surface).

In a preferred embodiment of the present invention, lateral surface 1104of the convex portion of the mold may be surface irregularities insteadof being smooth. As a result of these protrusions, the inner peripheralsurface of the concave portion of the ceramic substrate also has surfaceirregularities instead of being smooth. These surface irregularitieshave the effect of scattering light radiated from an LED chip, enablinglight to uniformly travel across the entire area separated by thepartition.

The mold of the present invention has a groove 128 on the distal endsurface of the convex portion. As a result of having this groove, thegreen sheet on the bottom of the concave portion of the green sheetenters the groove to form a partition when the convex portion is pressedinto the concave portion of the green sheet. The shape of this groove ispreferably a groove in the shape of a straight line or curved lineextending from a single point on the distal end surface 124 of theconvex portion toward another point on the distal end surface, or agroove in the shape of a straight line or curved line extending from asingle point on the distal end surface 124 of the convex portion towarda plurality of other points on the distal end surface. For example, anexample of a first shape of the groove is an I-shaped groove, while anexample of a second shape of the groove is a Y-shaped groove. An exampleof a third shape of the groove is a +-shaped groove (see FIGS. 13 and14). In the present invention, the shape of the groove is not limited tothe first to third shapes above, but rather can have various shapes.

As shown in FIG. 13C, a wall 1108 of the groove may preferably beinclined so that the width of the groove increases toward the directionof the opening of the groove in order to incline the wall of thepartition. The angle of inclination θ2 formed with the lateral surface1108 of this groove (see FIG. 13C) is preferably 50 to 70 degrees. Thewall of the partition is also inclined corresponding to the incline ofthe lateral surface 1108 of this groove. This incline of the partitionwall has the effect of reflecting light radiated from an LED chip andguiding it to the opening. In addition, surface irregularities may beformed in at least the lateral surface 1108 of the groove 128. As aresult of composing in this manner, surface irregularities can be formedin the partition during the pressing of step (v) of the previouslydescribed production process of the present invention (firstembodiment).

In a fourth embodiment of the production process of the presentinvention, in the case of a mold that presses a first ceramic sheet, itis not necessary to provide the groove 128 in the apex of the convexportion as shown in mold 114 of FIG. 4D.

The mold is provided with a gap 1102 between the base portion 122 andthe insertion portion 118, and the insertion portion 118 is able toslide in a direction perpendicular to the base portion 122 (see FIG.14C). This gap 1102 is preferably 1 to 100 μm, and more preferably 10 to50 μm. This is so that the insertion portion 118 does not slide from thebase portion 122 under normal conditions, but is able to slide whenconsiderable pressure is applied to the back of the insertion portion118. In addition, if this gap is excessively large, the green sheet endsup being pushed into the gap, thereby preventing the obtaining of thedesired shape of the ceramic substrate, while if the gap is excessivelysmall, an excessively large amount of pressure is required to cause theinsertion portion to slide. The use of the mold of the present inventionenables the insertion portion 118 to be pressed independently of thebase portion 122, resulting in each concave portion being presseduniformly. Thus, during the pressing of step (v) of the productionprocess of the present invention, the bottom 306 of the concave portionbecomes flat after pressing despite any protrusions on the surface ofthe green sheet. In this manner, in order to adequately press convexportion 116 of the mold into a concave portion of the green sheetsubstrate, it is effective for the convex portion 116 to slide in thedirection in which pressure is applied independently of the base portion122 by virtue of gap 1102 when pressure has been applied from the backof the mold.

Moreover, if a mold is used that allows insertion portion 118 to slideindependently of base portion 122, in the case a groove 128 is presentin the distal end surface 124 of a convex portion, a portion of thegreen sheet is reliably filled into that groove, thereby enabling apartition to be formed reliably.

Although FIGS. 13 and 14 show the example of the convex portion of themold having the shape of a circular truncated cone (namely, the shape ofthe distal end surface 124 is circular), the present invention is notlimited thereto. The shape of the convex portion may be a shape thatallows the obtaining of a desired concave portion 304 of a ceramic LEDpackage. For example, when viewed from the distal end surface 124 of theconvex portion, the shape of the distal end surface 124 may be oval,rectangular and so forth.

In the mold of the present invention, the lateral surface 1104 of theconvex portion preferably is inclined at a predetermined angle (θ1). Inthe present invention, the angle (θ1) formed by lateral surface 1104 ofthe convex portion and a plane extending along a straight line from thedistal end surface 124 of the convex portion (portion indicated withbroken lines in FIG. 14B) is preferably 10 to 89 degrees. Furthermore,even in the case of having a distal end surface of various shapes otherthan a circular shape as described above, the lateral surface is stillpreferably inclined at the above-mentioned angle (θ1).

In addition, the mold of the present invention may have a plurality ofinsertion portions in a single base portion. A composition comprising abase portion and a plurality of insertion portions is as previouslydescribed.

In particular, each insertion portion is able to slide perpendicularlyto the base portion due to a gap present between each insertion portionand an insertion portion housing portion. Thus, the problem of allconcave portions not being pressed uniformly, due to variations in thepressure applied to the back of the mold or slight variations in theshape of the concave portion of the ceramic green sheet substrate, canbe overcome. If all concave portions are not pressed uniformly, problemssuch as the back rising up in some of the concave portions or apartition not being formed in other concave portions may occur, thushaving an effect on yield.

When pressing the mold into a green sheet, the distal end surface of aninsertion portion of the mold adheres to the surface of a green sheet,air enters the groove in the distal end surface of the insertion portionof the mold and ends up being trapped therein. However, this air ispressurized and contracted by the pressing of the mold. Thus, entry ofthe green sheet into the groove to form a partition is not impaired.However, since a void is formed between the back of the groove and thesurface of the green sheet corresponding to the air compressed at thistime, the shape of the partition does not match the shape of the groove,but rather has a shape that differs somewhat from the shape of thegroove. Accordingly, it is preferable to set the groove of the mold andthe conditions for pressing the mold so that a partition height isobtained that enables it to demonstrate the function of blocking lightradiated from an LED chip.

In the case of applying a hydrostatic press, the above-mentioned problemof air being trapped in the groove of the mold is overcome since themold and green sheet are placed in a water-impermeable bag prior topressing and drawing a vacuum within the bag.

In the fourth embodiment of the production process of the presentinvention, a mold 114′ as shown in FIG. 4G or FIG. 4H is used in thecase of a mold that presses a second ceramic green sheet (second mold).This mold 114′ is a flat board and has a plurality of groove on oneside, and the groove is provided for forming a partition on one side ofthe second ceramic green sheet. The groove 128 is as previouslydescribed.

Next, an explanation is provided of a production process of the mold ofthe present invention using FIG. 15. FIGS. 15A and 15B are a perspectiveview and overhead view of a substrate serving as a base portion, FIGS.15E and 15F are a perspective view and overhead view of a substrate inwhich an insertion portion housing portion has been formed in thesubstrate, FIG. 15E is an overhead view depicting an insertion portion,and FIG. 15F is an exploded view depicting the insertion portion and thebase portion.

As shown in FIGS. 15A and 15B, the base portion 122 is fabricated byproviding the insertion portion housing portion 120 in one substrate1302 (thickness: 3-5 mm) by an ordinary means such as punching (seeFIGS. 15C and 15D). Next, the insertion portion 118 is fabricated inaccordance with standard methods for fabricating a mold such that theinsertion portion 118 has a maximum diameter that is about 20 μm smallerthan the diameter of the insertion portion housing portion 120 (see FIG.15E). The resulting insertion portion is then inserted into theinsertion portion housing portion of the base portion. Whenpress-forming a ceramic green sheet having a plurality of concaveportions all at once, the mold is also provided with a plurality ofinsertion portions 118 corresponding to the number of concave portions.Accordingly, a plurality of insertion portion housing portions may beprovided in an iron plate and insertion portions may be inserted intothe insertion portion housing portions, respectively. A gap of 1 to 200μm is present between the inner peripheral surface of the insertionportion housing portion of the base portion and the outer peripheralsurface 1304 of the portion of the insertion portion housed in the baseportion. In the case of a gap having these dimensions, the insertionportion 118 does not slide from the base portion 122 under normalconditions. As a result of applying pressure such as pressure of 1 to 50MPa, the insertion portion slides perpendicular to the base portion. Thematerial of the mold of the present invention is required to haverigidity that prevents it from being deformed as a result of applyingpressure and not deform at least under conditions of a temperature of 10to 150° C. and pressure of 1 to 50 MPa. More specifically, examples ofmaterials used for the base portion and insertion portion include iron,aluminum, copper, brass, stainless steel and alloys thereof.

EXAMPLES

Ceramic Green Sheet Substrate Lamination Step

Four LTCC ceramic green sheets measuring 75 mm long, 75 mm wide and 0.3mm thick were used for the ceramic green sheet substrate. Two of thesheets were used for the upper layer of the ceramic green sheetsubstrate, while the other two sheets were used for the lower layer. Thetwo green sheets for the upper layer of the ceramic green sheetsubstrate were superimposed, and four round through holes having adiameter of 5.2 mm were formed therein with a punch. Next, two ceramicgreen sheets not having through holes were superimposed, electricallyconductive paste was printed at the required locations corresponding tothe locations where LED chips are to be mounted, and allowed to dry. Thetwo ceramic green sheets having through holes were then superimposed onthe two ceramic green sheets not having through holes but printed withelectrically conductive paste as described above. The through holes ofthe ceramic green sheets of the upper layer serve as concave portions ofthe ceramic substrate.

Green sheet properties: sheet density: about 2 g/cm³, tensile strength:about 100 to 140 g/mm², surface roughness (Ra): <1 μm, minimum bendingradius: >2 mm (under 20° C.), 1 to 2 mm (20 to 30° C.), <1 mm (30 to 50°C.)

Post-firing ceramic properties: aluminum oxide/titanium oxide powdercontent, density: about 2.9 g/cm³, surface roughness (Ra): <1 μm,visible light reflectance rate: >90%, bending strength: about 200 MPa at0.3 mm thickness.

Press Forming Step

An iron plate having a thickness of 3 mm was placed on the back of theceramic green sheet substrate, a brass mold was inserted onto the frontof the ceramic green sheet substrate, and a ceramic green sheetsubstrate interposed between the base plate and the mold was placed in awater-impermeable bag (PTS bag, 250 mm long×175 mm wide, Mitsubishi GasChemical Co., Inc.). The insertion portion of the mold was in the shapeof a circular truncated cone in which the angle θ1 formed between thebottom of the base portion and the lateral surface of the insertionportion was 60 degrees, while the distal end surface of the insertionportion was circular having a diameter of 5.2 mm, the base of theinsertion portion was circular having a diameter of 6.0 mm, and thelength of the inclined portion was 0.55 mm. +-shaped grooves, composedof two straight lines measuring 5.2 mm in length passing through thecenter of the distal end surface were provided at a depth of 0.4 mm inthe distal end surface of the insertion portion. In addition, a 15 μmgap was present between the insertion portion and the base portion.Next, a vacuum was drawn within the bag with a vacuum packing machine(V-280, Tosei Electric Corp.). The ceramic green sheet substrate and themold were then pressed with a hydrostatic press (Hot Water Laminator,Nikkiso Co., Ltd.) while still contained in the water-impermeable bag.The pressing conditions at that time consisted 70° C. at 10 MPa for 10minutes. In addition, the pressed ceramic green sheet substrate and moldwere allowed to cool on standing to room temperature following pressingafter which the green sheet compact was separated from the mold.Furthermore, prior to pressing, a small amount of release agent in theform of silicone oil and the like was applied to the surface of the moldand base plate to facilitate separation from the green sheet afterpressing.

Ceramic Green Sheet Substrate Firing Step

Simultaneous to crimping the green sheets with the hydrostatic press,the lateral surfaces of the concave portions of the ceramic substratewere inclined by the mold and a +-shaped partition was formed in thebottoms of the concave portions. Subsequently, the crimped ceramic greensheet was fired in a box oven at a heating rate of 100° C./hr andholding at a temperature of 870° C. for 1 hour.

As a result of going through the steps described above, a ceramic LEDpackage was formed having a +-shaped partition (having a length andwidth of about 4.5 mm and height of about 0.35 mm). The drawings areprovided to explain the production process.

1. A production process for making a surface-mounting ceramic LEDpackage, comprising the steps of: (i) preparing a first ceramic greensheet and a second ceramic green sheet and forming through holes in thefirst ceramic green sheet; (ii) forming LED connection electrodes in thefirst and/or the second ceramic green sheet; (iii) layering the firstceramic green sheet and the second ceramic green sheet to form a ceramicgreen sheet substrate having a concave portion; (iv) inserting a mold,which comprises a base portion that presses portions other than theconcave portion of the first ceramic green sheet of the ceramic greensheet substrate, and an insertion portion having a convex portion thatprotrudes from the base portion and presses the inside of the concaveportion of the ceramic green sheet substrate, into the concave portionof the ceramic green sheet substrate so that the distal end surface ofthe insertion portion contacts the bottom of the concave portion of theceramic green sheet substrate, the distal end surface of the insertionportion of the mold being provided with a groove for forming a partitionin the bottom of the concave portion of the ceramic green sheetsubstrate; (v) crimping the ceramic green sheets by pressing the moldonto the ceramic green sheet substrate while at the same timepress-forming into a shape in which a partition is formed in the bottomof the concave portion of the ceramic green sheet substrate and thelateral surface of the concave portion is inclined so as to spreadtoward the opening; and (vi) firing the crimped and press-formed ceramicgreen sheet substrate to form a ceramic substrate.
 2. The productionprocess for a surface-mounting ceramic LED package according to claim 1,wherein the step (ii) is a step (ii′), in which via holes are providedin the second ceramic green sheet, an electrically conductive paste isfilled into the via holes, and electrodes for achieving electricalcontinuity with an LED chip are formed in the surface of the secondceramic green sheet in contact with the first ceramic green sheet so asto cover the via holes, and the step (iii) is a step (iii′), in whichthe first ceramic green sheet is layered on the side of the secondceramic green sheet on which the electrodes have been formed to form aceramic green sheet substrate having concave portions.
 3. The productionprocess for a surface-mounting ceramic LED package according to any ofclaims 1, wherein the groove in the distal end surface of the convexportion of the mold extends in a straight line from one point on thedistal end surface of the convex portion to another point on the distalend surface, or a plurality of grooves extend radially from a singlepoint on the distal end surface of the convex portion.
 4. The productionprocess for a surface-mounting ceramic LED package according to any ofclaims 1, wherein the lateral surface of the groove is inclined so as tospread from the bottom of the groove toward the opening to incline thelateral surface of the partition.
 5. The production process for asurface-mounting ceramic LED package according to any of claims 1,wherein the lateral surface of the groove has surface irregularities,thereby the surface of the partition is formed with surfaceirregularities.
 6. The production process for a surface-mounting ceramicLED package according to any of claims 1, wherein the mold is providedwith a gap between the base portion and the insertion portion, and theinsertion portion slides in a direction perpendicular to the baseportion.
 7. The production process for a surface-mounting ceramic LEDpackage according to claim 1, wherein the press-forming step comprisesthe steps of: placing the ceramic green sheet and the mold in awater-impermeable bag and drawing a vacuum inside the bag; and pressingthe bag in which a vacuum has been drawn by hydrostatic pressure orhydraulic pressure.